Synthesis of new bis-benzylidene-hydrazides as a sensitive chromogenic sensor for naked-eye detection of CN¯ and AcO¯ ions

Some new bis-benzylidene-hydrazides were synthesized via a condensation reaction of the corresponding azo dyes with adipic acid dihydrazide. All compounds because of the three possible stereoisomers showed four sets of signals in NMR. The anion recognition studies exhibited that the nitro bis-benzylidene-hydrazide derivative acts as a highly sensitive and selective chromogenic sensor for naked-eye detection of CN¯ and AcO¯ ions, with a distinct color change from yellow to blue and yellow to purple, respectively. The limit of detection (LOD) was found for 1d toward CN¯ to be 1.1?μM. The result of the Job's plot indicated stoichiometry of binding between chemosensor and anions is found to be 1:2.     

A biacylhydrazone-based chemosensor for fluorescence ‘turn-on’ detection of Al3+ with high selectivity and sensitivity

A simple Al³⁺ fluorescent chemosensor (1) based on diacylhydrazone has been designed and synthesized by the condensation reaction of 2-hydroxy naphthaldehyde and metaphthalic hydrazide. The chemosensor 1 displays a specific and sensitive response to Al³⁺ over other cations in DMSO solution. Upon the addition of DMSO solution of Al³⁺, the sensor 1 shows an immediate fluorescence ‘turn-on’ response and emitting strong blue emission with visible color change from colorless to green. The fluorescence quantum yield enhanced from 7.24% to 48.68%. Meanwhile, the fluorescence and UV absorption spectra detection limits of the chemosensor 1 for Al³⁺ were 2.0 × 10^?7 M and 5.6 × 10^?7 M respectively, indicating the high sensitivity of 1 to Al³⁺. Furthermore, test strips based on 1 were fabricated, which could be used as a convenient test kit for the detection of Al³⁺ and an efficient Al³⁺ controlled fluorescent security display materials.     

Construction of AIEgen functionalized nanomicelles and their stability study through ‘seesaw-like’ fluorescence changes

As nanocarriers, nanomicelles play vital roles in the toolbox of drug delivery. The stability of nanomicelles affects the nanomedicines’ bioactivity. Therefore, it is important to understand the stability of nanomicelles for further improvements. Here, we report a strategy to construct new nanomicelles (NM) by introducing aggregation-induced emission (AIE) functional group tetraphenylethylene (TPE) in the component polymer vitamin E (d-α-tocopheryl polyethylene glycol 1000 succinate) (TPGS). The stability of doxorubicin (DOX) loaded nanomicelles DOX@NM in different conditions was studied by fluorescence analysis. The fluorescence changes of DOX@NM are ‘seesaw-like’ when they transform between assembled and disassembled forms. In the assembled form, TPE gives emission from AIE effect, while in the disassembled form, the fluorescence of DOX is observed due to the disappearance of ACQ effect.     

Electrochemical and associated techniques for the study of the inclusion complexes of thymol and β-cyclodextrin and its interaction with DNA

Journal of Solid State Electrochemistry - Thymol, a potent agent for microbial, fungal, and bacterial disease, has low aqueous solubility and it is genotoxic, i.e., is capable of damaging...     

Optimized structures and vibration frequencies of the ether–water complex: a DFT and FTIR study

The infrared spectrum of ether was studied using Fourier transform infrared spectroscopy in conjunction with the density functional theory (DFT). The optimized structures and vibrational frequencies of the ether·(H₂O) _n (n = 1–3) complexes were obtained at B3LYP/6-31G(d) theory levels. Compared to those of free-form ether, the C–O stretching vibrational frequencies of the ether–water complexes are found to shift to red by up to 39 cm^?1 with an increase in the C–O length of 0.016 Å. Meanwhile, the frequency of the O–H stretching modes of water in the complexes appears significantly redshifted to a varying degree. The DFT calculations suggest that these shifts are caused by the hydrogen bonding between ether and water.     

Smart optical probe for ‘equipment-free’ detection of oxalate in biological fluids and plant-derived food items

A reversible ‘turn-on’ sensor has been designed for ‘naked-eye’ detection of oxalate at nanomolar concentration (～12.5?nM) at pH 7.4. The sensory system shows a highly specific response towards oxalate among a wide range of antinutrients and biologically relevant anionic species. Mechanistic investigations indicate that oxalate can turn the pink-colored solution colorless by dissociating the preformed metal complex. Additionally, high specificity and good accuracy with recovery values ranging from 93.3 to 105.0% were obtained during oxalate estimation in spiked water and human urine samples, confirming the suitability of the present method in estimating trace-level of oxalate in complex matrices. With these results, quantitative estimations of endogenous oxalate were achieved in more than twenty-five different agricultural crops. Finally, low-cost, portable paper strips were developed for on-site detection of oxalate.     

HPLC-spectrophotometric detection of trace heavy metals via ‘cascade’ separation and concentration

A cascade pre-concentration and separation system involving continuous solid-phase extraction and one-drop solvent concentration was developed to enable high-performance liquid chromatography (HPLC) determination of trace levels of Ni(II), Co(II), Cu(II), Se(IV) and Cr(VI) ions in aqueous solution via complexation with sodium diethyldithiocarbamate. The metal complexes were almost completely adsorbed on the solid phase (octadecylsilyl packed column). Ethyl acetate (eluent) containing the metal complexes was then placed in a centrifuge tube, to which a microvolume of dimethyl sulfoxide (DMSO) was added. Successful pre-concentration of the metal complexes into the DMSO phase was accomplished by removing the ethyl acetate using a compact evaporator in a water bath (40°C); 1000-fold concentration was achieved within 45 min. A portion of the residual DMSO phase was then subjected to HPLC analysis. The proposed method has high reproducibility and high sensitivity with detection limits (3σ) for Ni(II), Co(II), Cu(II), Se(IV) and Cr(VI) ions of 0.08, 0.11, 0.12, 0.44 and 0.20 µg/L, respectively. Relative standard deviations (RSDs) (n = 5) at Ni(II) 5.87 µg/L, Co(II) 5.89 µg/L, Cu(II) 6.35 µg/L, Se(IV) 7.90 µg/L and Cr(VI) 5.20 µg/L (1.0 × 10^?7 mol/L each) were 4.0%, 4.6%, 4.6%, 7.2% and 3.4%, respectively.     

Production of chiral matrices with hybrid silver–thiocholesterol nanosystems and study of their properties

A new type of chiral matrix based on silver–thiocholesterol hybrid nanosystems adsorbed on silica gel has been proposed. The molar ratio of stabilized thiocholesterol (L) ligand and silver (Ag) was found to have little effect on the size of the resulting silver nanoparticles (SNPs). The average diameter of SNPs was 2.7 ± 0.4, 2.2 ± 0.4, and 2.1 ± 0.6 nm upon the ratios Ag: L = 1: 5, Ag: L = 1: 2, and Ag: L = 1: 0.5, respectively. The resulting chiral matrices possess enantioselectivity relative to the 1,1’-binaphthyl-2,2’-diamine (BNDA) and trifluoroanthranyl ethanol (TFAE) optical isomers. The TFAE optical isomers were successfully separated using thin layer chromatography (α = 1.56).     

Synthesis and structure of a ‘4 + 1’ oxorhenium(V) complex containing imidazole derivatives

The ‘4?+?1’ concept was used to prepare the complex salt [ReO(iao)Br]Br (1) from the reaction of (n-Bu₄N)[ReOBr₄(OPPh₃)] with the ligand bis{2′-methyl(1′-methylimidazole)}-2-aminoethanol (Hiao) in methanol. The single-crystal X-ray crystal structure of 1 shows that iao acts as a monoanionic, tetradentate, N₃O-donor chelate. When the reaction was carried out in acetonitrile, the neutral complex [ReO(iao)Br₂] (2) was isolated. Elemental analyses and IR data suggest that iao acts as a tridentate, N₂O-donor ligand in 2.     

EPR and DFT study of the ethylene reaction with O− radicals on the surface of nanocrystalline MgO

Research on Chemical Intermediates - Different radical forms of oxygen (O?, O 2 ? and O 3 ? ) on the surface of nanocrystalline MgO are well known. It was earlier demonstrated...     

Preparation and characterization of the inclusion complex of baicalein with γ-cyclodextrin: an antioxidant ability study

The formation of the complex of Baicalein with γ-cyclodextrin (γ-CD) was studied by UV–Vis absorption spectroscopy, fluorescence spectra and nuclear magnetic resonance spectroscopy (NMR) in solution. The solid inclusion complex of Baicalein with γ-CD was synthesized by the co-precipitation method. The characterization of the solid inclusion complexes have been proved by infrared spectra. The formation constant (K) of complex was determined by fluorescence method. The results suggested that in different pH solutions, γ-CD has different inclusive capacity to different forms of Baicalein. γ-CD was most suitable for inclusion in neutral media. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of Baicalein with γ-CD. Kinetic studies of DPPH? with Baicalein and γ-CD complex were done. The results obtained indicated that the Baicalein/γ-CD complex was the most reactive form. Special configuration of complex has been proposed on NMR technique.     

Detection of cyanide (CN−) ion with high selectivity and sensitivity by using ‘Turn-ON’ fluorescence strategy of Rhodamine Schiff base

A Rhodamine based Schiff base, (E)-3′,6′-Bis(ethylamino)-2-(2-(((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methyl-ene)amino)ethyl)-2′,7′-dimethylspiro[isoindoline-1,9′-xanthen]-3-one (HL) has been synthesized and characterized by various spectroscopic data, viz. ¹H and ¹³C NMR, ESI-MS, FT-IR and elemental analysis. It shows very weak fluorescence emission (9:1 (v/v) DMSO/H₂O, HEPES buffer at pH 7.4) while it is enhanced considerably upon addition of CN⁻ ion selectively (λ_em, 456 ​nm) in presence of nineteen other biologically important anions. The Limit of Detection (LOD) is 24 ​nM which is significantly lower than literature reported data. The binding interaction of the probe to CN⁻ ion, 1:1 (HL:CN⁻) mole ratio has been confirmed by Job's plot, ESI-MS spectral data and ¹H NMR spectral titration measurement.     

Bithiophene triarylborane dyad: An efficient material for the selective detection of CN− and F− ions

A new fluorescent chemosensor based on bithiophene coupled dimesitylborane (BMB-1) was synthesized and characterized. BMB-1 was used for colorimetric and turn-on fluorescent sensing of cyanide (CN⁻) and fluoride (F⁻) ions, in the presence of other competitive anions in an aqueous (CH₃CN–H₂O) medium. BMB-1 showed a hypsochromic shift (blue shift) with addition of CN⁻ and F⁻ ions in absorption studies. The lower detection level of CN⁻ and F⁻ ions is 1.37 × 10⁻⁹ and 1.75 × 10⁻⁹ M, respectively. The BMB-1 binding mechanism is based on the nucleophilic addition of CN⁻ and F⁻ ions in the internal charge transfer transition of bithio moiety to the boranylmesitylene unit, and the color changes were observed under UV light. This result is further confirmed by Fourier transform infrared spectroscopy, mass spectrometry and density functional theory calculations. Also, the BMB-1 probe is found to be a good adsorbent for the removal of F⁻ ions in real water samples using the adsorption technique.     

A highly selective fluorescent chemosensor for successive detection of Fe3+ and CN− in pure water

A water-soluble fluorescent chemosensor (D) based on 1, 8-naphthalimide derivative has been designed and synthesised as a new fluorescent sensor for successive detection of Fe³⁺ and CN^?. Fluorescence measurements show that chemosensor D has excellent fluorescent-specific selectivity and high sensitivity for Fe³⁺ over many other metal ions in pure water. Moreover, the complex of D and Fe³⁺ (D–Fe³⁺) displayed high sensitivity for CN^? over many other anions in the same medium. Even more important, the recognition of the sensor D for Fe³⁺ and D–Fe³⁺ complex for CN^- could be used successfully in pure water. The test strips based on D and D–Fe³⁺ exhibited good selectivity to Fe³⁺ and CN,^- respectively, we believe the test strips could serve as convenient and efficient Fe³⁺ and CN^? test kits.     

Exploration of superhalogen nature of Pt(CN)n complexes (n = 1–6) and their abilities to form supersalts and superacids: a DFT–D3 study

Structural Chemistry - Unique superhalogen properties of Pt(CN)n complexes (n = 1–6) have been investigated under the quantum chemical formalism. The study involves theoretical calculations...     

Isomer selective IR-UV depletion spectroscopy of 4-fluorotoluene-NH3: evidence for π-proton-acceptor and linear hydrogen-bonded complexes

The 4-fluorotoluene-ammonia van der Waals complex has been studied using IR-UV depletion and hole-burning spectroscopies with assignments supported by ab initio and DFT calculations of ground state binding energies and intramolecular vibrational frequencies. The experimental IR-UV depletion and hole-burning spectra presented here provide unequivocal empirical evidence that the 4FT-NH(3) complex exists in two almost equally stable conformational forms. Both isomers contribute intensity to the experimental R2PI spectrum with one responsible for bands appearing to the red of the 4FT band origin position, and the other for those appearing immediately to the blue. On the basis of comparison of computed NH stretching frequencies with those obtained from the IR-UV spectra, the red-shifted bands are assigned to a π-proton-acceptor complex featuring an NH···π-hydrogen bond, and the blue-shifted bands are assigned to an in-plane σ-complex in which the ammonia binds in the plane of the ring forming a double-hydrogen-bonded six-membered ring with the fluorine atom. Ground state interaction energies computed at the M06-2X/cc-pVTZ level were found to compare favourably with those obtained at the CCSD(T) CBS level, although the former resulted in overbinding of the π-complex compared with the in-plane conformer, a characteristic shared with MP2 level calculations. The observation of a π-complex in addition to a σ-complex is consistent with the conclusion that the electron-donating power of the methyl group is sufficiently large to counter-balance the electron-withdrawing power of the fluorine atom.     

A zerovalent nickel-2,2′-bipyridine complex: an efficient catalyst for electrochemical homocoupling of ortho-substituted halides and their heterocoupling with meta- and para-substituted halides

Electroreduction of ortho-substituted halides ArX in a nickel-2,2′-bipyridyl system and N-methylpyrrolidone as solvent gave the homocoupling product ArAr. The nickel-2,2′-bipyridyl system is also a catalyst for the electrochemical heterocoupling of ArX with meta- or para-substituted halides Ar′X′.     

Preparation and characterization of zein/chitosan complex for encapsulation of α-tocopherol, and its in vitro controlled release study

Chitosan (CS) nanoparticles coated with zein has been newly demonstrated as a promising encapsulation and delivery system for hydrophilic nutrient with enhanced bioactivities in our previous study. In this study, a hydrophobic nutrient, α-tocopherol (TOC), was successfully encapsulated into zein/CS complex. The fabrication parameters, including zein concentration, zein/CS weight ratio, and TOC loading percentage, were systematically investigated. The physicochemical and structural analysis showed that the electrostatic interactions and hydrogen bonds were major forces responsible for complex formation. The scanning electron microscopy study revealed the spherical nature with smooth surface of complex. TOC encapsulation was also evidenced by differential scanning calorimetry. The particle size and zeta potential of the complex varied from 200 to 800 nm and +22.8 to +40.9 mV, respectively. The kinetic release profile of the TOC showed burst effect followed by slow release. Compared with zein nanoparticles, zein/CS complex provided better protection of TOC release against gastrointestinal conditions, due to CS coatings. Zein/CS complex is believed to be a promising delivery system for supplementation or treatment of hydrophobic nutrients or drugs.